The present invention relates to a tool intended for metal chip-breaking machining.
Such tools are known which comprises a body that is rotatable around a central geometrical axis, said body having a peripheral envelope surface in which one or several recesses are delimited by a bottom wall, and leading and trailing walls which diverge outwardly from the bottom wall. Each one of said recesses has the purpose of accommodating on one hand a cartridge having a cutting insert provided in a seat in said cartridge, and on the other hand a clamping wedge intended for fixing the cartridge. The wedge is tightenable by means of a clamping screw in engagement with a threaded hole that extends into the bottom wall in the body. The trailing wall of the recess has first serrations provided to cooperate with analogous second serrations formed on a trailing side of the cartridge opposed to the cutting insert. The leading wall of the recess is smooth in order to cooperate with an equally smooth leading surface of the clamping wedge. A trailing contact surface of the clamping wedge and a leading contact surface of the cartridge are both smooth in order to, when in contact with each other, permit a substantially radial displacement of the clamping wedge relative to the cartridge in connection with the fastening of the latter.
In particularxe2x80x94although not exclusivelyxe2x80x94the invention relates to milling tools, e.g., square shoulder facemills, facemills, slitting cutters or the like.
A tool realized in the shape of a milling cutter of the type as generally described above, is previously known from SE 9103724-2 (corresponding to U.S. Pat. No. 5,395,186). In this case, the individual cartridge can be introduced into the appurtenant recess from either the front or the back of the tool body, the determination of the axial position of the cartridge relative to the recess being adjusted by means of a radially oriented pin provided on the lower side of the cartridge, which pin is arranged to engage into a depression formed in the bottom wall of the recess, said depression having a larger diameter than the pin. Furthermore, each individual cutting insert is fastened on the appurtenant cartridge by means of a headed screw that extends through a through-hole in the cutting insert and is tightened into a threaded hole in the cartridge. The fact that the construction includes both a clamping wedge for fixing the cartridge per se, and a particular clamping screw for fixing the cutting insert on the cartridge, in practice means that the tolerance chain between on the one hand the tool body and its axis of rotation, and on the other hand each one of the numerous cutting inserts, becomes long. Inter alia, this leads to a situation where the precision of the positioning of the cutting inserts relative to the tool body (which in practice should be less than {fraction (1/100)} mm) may easily be lost or become unsatisfactory, e.g., when the cutting inserts are to be replaced or indexed, or when for any reason, the cartridge has to be dismounted and remounted. In addition thereto, the task of fine-adjusting the cutting inserts and the appurtenant cartridges relative to the tool body is tedious and time-consuming, something that is particularly disturbing when the milling tool is to operate at high speeds of rotation and/or to cut tough materials, which gives limited life of the cutting edges of the inserts and, thereby, necessitates frequent replacement or indexing of the cutting inserts.
The present invention aims at eliminating the above mentioned inconveniences of previously known tools of the type in question and creating an improved tool, in particular a milling tool. Thus, a primary object of the invention is to provide a tool with detachable cutting inserts which may be fixed in seats in appurtenant cartridges without the use of means other than the clamping wedges that are used for the fixing of the cartridges in the peripheral recesses of the tool body.
A further object is to provide a tool in which the individual cartridge as well as the appurtenant cutting insert are capable of, with ease, assuming exactly defined operative positions relative to the tool body in connection with the mounting of, on one hand, the cartridge in the recess and, on the other hand, the cutting insert in the cartridge seat. Another object is to create a tool with a good ability to withstand at least minor break-downs in connection with, e.g., instantaneous and abrupt impact and shock loads.
In particular, the cartridge should be capable of resisting such loads without being seriously damaged or dislocated from its basic position. still another object of the present invention is to provide a tool particularly intended for milling purposes, which may work at very high speeds of rotation, e.g., up to the range of 20,000 to 30,000 rpm. One particular aspect of the invention aims at providing a tool whose cutting inserts are secured centrifugally in a reliable way, even when the tool is caused to rotate at very high speeds of rotation.
According to the invention, at least the primary object is achieved by providing a clamping wedge with two separate contact surfaces. One of the clamping surfaces functions to press an insert-carrying cartridge into a respective recess of a tool body, and the other contact surface functions to press the insert into its insert sea of the cartridge while also pressing the cartridge into its recess.